Dynamic Numerical Simulation About Rock Borehole Fracturing And Propagation Of Fractures

Improving reservoir physical properties is one of the most effective approaches for exploitation of low permeability layer. Properties of low permeability layer can be improved by virtue of explosion. Especially, the permeability will be enhanced, so the mechanism of rock breakage induced by explosion should be studied in depth. The rock fracturing mode under the condition of explosion including exploding wave and the exploding gas belongs to the dynamical fracturing, In this paper, based on the importance of exploding gas, the mechanism and rules about rock fracturing caused by exploding gas is studied.In order to study the rock fracturing and propagation of fractures within a cavity induced by exploding gas, the mechanics modal containing samples inertia is established according to experiment analysis. On the ground of this mechanics modal, the mechanism that causes more fractures under the condition of dynamic load is also studied by means of dynamic numerical simulation. Moreover, experiment analysis shows that initial damages and loading rate have some effect on rock fracturing and propagation of initial fractures. So in this paper, the radial fractures with different length and position around a borehole wall are considered to be the only initial damages in the samples. Based on these hypothesises, the rules of rock fracturing and influencing factors are studied.Experiment and simulation results reveal that creating more fractures within a cavity caused by exploding gas is a kind of structural response.Creating more fractures is determined by load,restraint,structure,material attribute and other factors.Furthermore,regulations about fracturing and propagation about fractures under the condition of different loading rate and initial damages are also obtained in this paper.In a word, the initial fractures with different position and length will influence quantity and location of new fractures on the hole wall. More higher loading rate is helpful for creating more new fractures on the borehole wall.These results will be helpful not only for further research of"reservoir explosion"and optimum project designs, but also for solution stability of numerical analysis and the compound technique of perforating and high-energy gas fracturing.